Not Applicable
Not Applicable
Not Applicable
1. Field of the Invention
This invention is in the field of optical component measuring and testing and, more particularly, is in the domain of quantitative measurement of lens and mirror power and other optical characteristics.
2. Description of the Prior Art
Optical components for precision applications, such as lenses and mirrors, are now being mass-produced in ever increasing quantities. Many are made by molding monomeric or polymeric materials such as polycarbonates. Some of these materials are cured by heat or exposure to ultra-violet light. Because the molding and curing steps in the manufacturing process cannot be controlled as tightly as required by specifications for new lenses, a need has arisen for a new system and method for measuring properties of optical components at production-line speeds.
One type of precision optical component being manufactured in ever-increasing quantities is the soft contact lens. A high-speed cosmetic defect detection system for contact lenses is taught in European Patent No. EP0882969; however, this system cannot measure power or other optical properties.
Another high-volume precision ophthalmic product is the progressive multifocal ophthalmic spectacle lens of the type described in U.S. Pat. No. 6,102,544. FIG. 1 of that patent is a diagrammatical front view of a progressive multifocal ophthalmic lens comprising three regions of different power. These regions are defined in that patent as a far vision region VL, a near vision region, VP and an intermediate region between the two other regions, VI. The ""544 patent defines a reference point for measuring far vision power, L, and a reference point for measuring near vision power, P. The powers measured at reference points L and P define major properties of these lenses.
Progressive spectacle lenses are manufactured at rates of approximately one per second. They are ejected from molding machines in random orientations of the reference points for far vision L and near vision P. This complicates the task of measuring powers at reference points L and P.
Prior art lens meters commonly used at manufacturing sites are manually operated instruments. They can be classified as those that a] measure refraction of one or more beams of light (e.g. U.S. Pat. No. 5,489,978) or b] generate patterns. Of the later, there are some that generate moirxc3xa9-effect patterns, (e.g. U.S. Pat. No. 5,872,625).
Moirxc3xa9-effect patterns are generated by superimposing a repetitive design, such as a grid, on the same or a different design in order to produce a pattern distinct from its component designs. Examples are described in Amidror, The Theory of the Moirxc3xa9 Phenomenon, Kluwer Academic Publishers, Norwell, Mass. (copyright)2000. Problem 2-27. Testing lenses cites Oster and Nishijima, xe2x80x9cMoirxc3xa9 Patternsxe2x80x9d, Scientific American, May 1963, pp. 54-63, that contains an example of moire-effect rotation when positive and negative optical lenses are placed between a pair of linear-ruled plates.
In order to use a conventional lens meter, an operator first must orient each lens with respect to a lens meter. Then, the operator must make two separate measurementsxe2x80x94one for far vision (base) power at reference point L and another for near vision (add) power at reference point P on a lens before the lens is packaged. Each of these two measurements must be accurate to within xe2x85x9 diopter to be commercially useful. However, the accuracy of the measurement can be degraded if an operator selects a measurement point other than L or P. This can readily happen for lenses with low add powers at reference points P or if the inspector has a visual acuity deficiency. Manual inspection is not economical for such high-speed inspection because it is too slow, because human inspectors are prone to making biased judgments and because inspection results among different inspectors are not uniform.
One principal obstacle to automatic inspection of optical components has been the difficulty of generating rapidly a comprehensive map of component optical properties, such as power at each point on the component""s optical surface.
Another principal obstacle to automatic inspection of optical components has been the requirement that the component be oriented in a preferred position before measurements can be obtained with instrumentsxe2x80x94such as lensometersxe2x80x94of the prior art.
It is therefore an object of the present invention to provide a robust in situ system and method for measuring properties, such as power, of optical components, such as lenses and mirrors.
A second object of this invention is to provide a system and method for measuring properties of an optical component without requiring that the component be rotationally oriented in a preferred position about its optical axis before measurements can be obtained.
A third object of this invention is to provide a system and method for generating rapidly a comprehensive moirxc3xa9-effect map of component optical properties, such as power at each point on the component""s optical surface.
A fourth object of this invention is to provide an accurate system and method for analyzing maps of component optical properties so as to be able to measure power and other variables for the entire component.